Ascorbic acid exhibits the effect of preventing aging of skin since ascorbic acid exhibits the function of antioxidation and takes part in forming and maintaining collagen. Therefore, ascorbic acid is used for skin whitening products as a component for preventing formation of spots and freckles, i.e., a safe raw material for skin whitening.
Ascorbic acid is used also as a drug for supplementing vitamin C and a drug for curing pigmentation, drug intoxication and adrenal cortex dysfunction.
Ascorbic acid is used also in cooling drinks, preserved foods, cookies and healthy foods.
However, when ascorbic acid is dissolved in water, ascorbic acid is very unstable and easily oxidized in the presence of light, heat or metal ions or depending on pH. It is difficult that an aqueous solution of ascorbic acid in a great concentration is stored with stability when such a solution is prepared.
The present inventors considered that the applications described above could be expanded and new applications could be found when a solution of ascorbic acid in an organic solvent which contained ascorbic acid in a great concentration and was stable could be prepared. A process for producing a solution containing 16 to 45% by mass of ascorbic acid in glycerol had been developed, and the patent application was made.
Heretofore, it is known that ascorbic acid can be dissolved in glycerol to the maximum concentration of 15% by mass (refer to Patent Reference 1).
The concentration of ascorbic acid in the glycerol solution obtained in accordance with the above process developed by the present inventors is 16 to 45% by mass.
When the glycerol solution containing ascorbic acid in the concentration as great as that described above is used as the base material for cosmetics, it is desired that the feel in the use (spreadability and smooth feel on application to the skin) of the solution is further improved.
[Patent Reference 1] Japanese Patent Application Laid-Open No. 2004-155733